/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.expression;

import org.springframework.core.convert.TypeDescriptor;
import org.springframework.lang.Nullable;
import org.springframework.util.ObjectUtils;

/**
 * Encapsulates an object and a {@link TypeDescriptor} that describes it.
 * The type descriptor can contain generic declarations that would not
 * be accessible through a simple {@code getClass()} call on the object.
 *
 * @author Andy Clement
 * @author Juergen Hoeller
 * @since 3.0
 */
public class TypedValue {

    /**
     * {@link TypedValue} for {@code null}.
     */
    public static final TypedValue NULL = new TypedValue(null);


    @Nullable
    private final Object value;

    @Nullable
    private TypeDescriptor typeDescriptor;


    /**
     * Create a {@link TypedValue} for a simple object. The {@link TypeDescriptor}
     * is inferred from the object, so no generic declarations are preserved.
     *
     * @param value the object value
     */
    public TypedValue(@Nullable Object value) {
        this.value = value;
        this.typeDescriptor = null;  // initialized when/if requested
    }

    /**
     * Create a {@link TypedValue} for a particular value with a particular
     * {@link TypeDescriptor} which may contain additional generic declarations.
     *
     * @param value          the object value
     * @param typeDescriptor a type descriptor describing the type of the value
     */
    public TypedValue(@Nullable Object value, @Nullable TypeDescriptor typeDescriptor) {
        this.value = value;
        this.typeDescriptor = typeDescriptor;
    }


    @Nullable
    public Object getValue() {
        return this.value;
    }

    @Nullable
    public TypeDescriptor getTypeDescriptor() {
        if (this.typeDescriptor == null && this.value != null) {
            this.typeDescriptor = TypeDescriptor.forObject(this.value);
        }
        return this.typeDescriptor;
    }


    @Override
    public boolean equals(Object other) {
        if (this == other) {
            return true;
        }
        if (!(other instanceof TypedValue)) {
            return false;
        }
        TypedValue otherTv = (TypedValue) other;
        // Avoid TypeDescriptor initialization if not necessary
        return (ObjectUtils.nullSafeEquals(this.value, otherTv.value) &&
                ((this.typeDescriptor == null && otherTv.typeDescriptor == null) ||
                        ObjectUtils.nullSafeEquals(getTypeDescriptor(), otherTv.getTypeDescriptor())));
    }

    @Override
    public int hashCode() {
        return ObjectUtils.nullSafeHashCode(this.value);
    }

    @Override
    public String toString() {
        return "TypedValue: '" + this.value + "' of [" + getTypeDescriptor() + "]";
    }

}
